What does 'Autorun disabled' statement mean?
Blender comes bundled with python. Malicious scripts written in python could potentially damage your computer. As a security measure the automatic running of python scripts has been disabled since version 2.6.
What this most likely means is that there is a piece of python code that is controlling the driver.
You can allow blender to auto run scripts by changing your user preferences. To do this press Ctrl + Alt + U, then head over to File and enable Auto Run Python Scripts. Although it is unlikely that someone will distribute a malicious blend file you should still make sure where you download .blend file from

More information on Scripting &amp; Security at the official documentation.